Method and devices for connecting an aluminum strip to a copper strip under protective gas

ABSTRACT

The invention relates to a method for a firm metallurgic connection of an aluminum band with a copper band through which the two bands that are moved relative to one another in their longitudinal direction are continuously cleaned from oxides in a cleaning device under protective gas at their contact surfaces and are subsequently provided to a compression device in which the bands are pressed together with their clean surfaces and connected with another to form a one-piece band including the steps: running both bands ( 8, 9 ) continuously under protective gas up to and into the compression device ( 4 ) by configuring the cleaning device ( 3 ) and the compression device ( 4 ) as a unit in a housing ( 7 ) enclosing a contiguous space, and pulling the two bands ( 8, 9 ) or the one piece band ( 11 ) through the cleaning device ( 3 ) and the compression device ( 4 ) by a pull off device ( 5 ) arranged behind (downstream) the compression device ( 4 ).

The invention relates to a method for a metallurgically firm connectionof an aluminum band with a copper band through which the two bands thatare moved relative to one another in their longitudinal direction arecontinuously cleaned from oxides in a cleaning device under protectivegas at their contact surfaces and are subsequently provided to acompression device in which the bands are pressed together with theirclean surfaces and connected with another to form a one-piece band. Theinvention also relates to a device for performing the method (EP 1 469486 B1).

A one-piece band made from two different metals produced through amethod of this general type is used in particular for high frequencyapplications. Through the known effect of current displacement, onlyrather thin copper layers are required in conductors of high frequencycables. The aluminum band connected with the copper band through thedescribed method is only used for stabilizing the copper band and as acarrier for the copper band. In order for the metallurgic connection tobe maintained, the bands and in particular the easily and quicklyoxidizing aluminum band have to be cleaned from oxides.

A method is known from U.S. Pat. No. 2,414,511 A through which two bandsthat are made from metal shall be connected with one another, One bandis for example made from steel and the other band is for example madefrom copper. The two bands are fed to a large volume housing in whichthey are cleaned and heated through flames. The bands thus treated arepressed together through rollers inside the housing to form a one-pieceband which subsequently exits the housing. In order for a band made fromcopper not to oxidize after cleaning and heating, a controlledatmosphere is maintained in the housing.

In the method according to EP 1 469 486 B1, recited supra, a copper bandand an aluminum band are cleaned from oxide layers in a cleaning deviceusing rotating brushes at flat sides for mutual contact using anprotective gas, for example argon.

The protective gas prevents a reformation of oxides. The two bands arethen run through a gap between two rollers of a roller arrangement andthus metallurgically connected. Simultaneously, the thickness of the onepiece band is reduced. The two bands and thus also the one piece bandare moved in their longitudinal direction by the driven rollers of theroller assembly. The protectiveial gas zone terminates at the outlet ofthe cleaning device used in this application. On a path of the two bandsfrom the cleaning device to the rollers of the roller arrangement, inparticular the aluminum band can oxidize quickly again so that acontinuous metallurgic connection with the copper band cannot beguaranteed.

It is an object of the invention to improve the method recited supra sothat a recurring oxide formation at both bands can be excluded beforejoining. The object is achieved according to the invention by performingthe following steps:

-   -   cleaning the two bands separately in separate housing        compartments of a contingent housing under protective gas, in        particular cleaning the two bands from oxide materials,    -   subsequently running the two bands to the compression device        under continuous protective gas coverage through channels        connected hermetically tight with the two housing compartments,    -   subsequently contacting the two bands under pressure in a        compression device enveloped by a proper housing connected with        the channels hermetically tight under continuous protective gas        coverage, and    -   pulling the two bands or the one piece band through the cleaning        device and the compression device through a pull off device        arranged behind the compression device.

The protective gas used in this method is a special gas which prevents aformation of oxides. Respective gases are for example noble gases, inertgases and reducing gases. Through using this method, a formation ofoxide layers on the two bands to be connected, in particular on thealuminum band, can be excluded, since the two clean bands are movedunder the protective gas until they are firmly contacted in thecompression device and pressed against one another. This is essentiallyfacilitated in that the dimensions of the compression device can be keptsmall because the two bands or the produced one piece band are not movedthrough driven large volume rollers but are pulled by a separate pulloff device. Accordingly, for example, two rotatably support rollers withrelatively small dimensions can be used in the compression device,wherein the rollers are separated from one another through an adjustablegap through which the bands are being pulled. For example also a slotnozzle with adjustable slot can be used for the compression device. Ahousing enclosing a compression device of this type can have rathersmall dimensions and can be easily connected with a housing enclosingthe cleaning device in order to form a one piece housing. The one piecehousing is filled with protective gas while the method is performed. Thecoverage of the two bands with protective gas preventing a formation ofoxide layers is only terminated according to this method when the onepiece band which is formed by metallurgically connecting the two bands,leaves the compression device.

The method according to the invention is subsequently described based onan embodiment with reference to drawing figures, wherein:

FIG. 1 schematically illustrates an arrangement for performing themethod according to the invention; and

FIG. 2 illustrates a detail of FIG. 1 in a more defined configuration.

The arrangement for connecting an aluminum band with a copper bandincludes two rotatably supported coils 1 and 2, a cleaning device 3, acompression device 4, a pull off device 5, and a wind up coil 6. Thepull off device 5 is advantageously configured as a track pull off, thecleaning device 3 and the compression device 4 are arranged in a commonhousing 7, which is filled with an inert gas when the method isperformed, for example filled with argon. A copper band 8 is wound ontothe bobbin 1, whereas an aluminum band 9 is wound onto the bobbin 2.Both bands 8 and 9 preferably have the same width.

The method according to the invention is performed for example asfollows.

The two bands 8 and 9 are pulled from their bobbins 1 and 2 in adirection of the arrow 10 and pulled through the cleaning device 3 andthe compression device 4. In the cleaning device 3, the mutual contactsurfaces of the two bands 8 and 9 are cleaned from contaminations and inparticular oxide materials in continuous operation. This is performedunder protective gas, so that no oxide layers can form on the cleansurfaces of the bands 8 and 9 after leaving the cleaning device 3. Inorder to maintain the protective gas coverage in the housing 7, itincludes sealed inlets for passing the two bands 8 and 9 through.

The two cleaned bands 8 and 9 are joined within the housing 7 undercontinued protective gas coverage in the compression device 4 andpressed against each other so that they are metallurgically connectedwith one another to form a one piece band 11, The one piece band 11exits the housing 7 through a sealed outlet. It can be subsequentlywound onto the bobbin 6.

The unit including the housing 7, the cleaning device 3 and thecompression device 4 is configured according to FIG, 2. The housing 7illustrated in one piece in FIG. 1 is divided into components connectedwith one another in the embodiment according to FIG. 2. The cleaningdevice 3 accordingly includes an upper housing component 12 and a lowerhousing component 13. In both housing components 12 and 13, a pluralityof grinding discs or metal brushes 14 or 15 is arranged that isrotatable about an axis. The compression device 4 includes a properhousing 16. The two housing elements 12 and 13 of the cleaning device 3are connected hermetically tight through channels 17 and 18 with thehousing 16 of the compression device 4 so that the integral contiguousspace that is filled with protective gas is implemented which isdesignated in FIG. 2 through a dash dotted line which corresponds to thehousing 7 according to FIG, 1. According to FIG. 2, the cleaning device3 and the compression device 4 are passed through by the bands 8 and 9,for example as follows.

The copper band 8 initially enters the housing element 12 of thecleaning device 3 while the aluminum band 9 is pulled through the lowerhousing element 13 of the cleaning device 3. The copper band 8 is thusfor example pulled along metal brushes 14, while the aluminum band 9 isadvantageously pulled along grinding discs 15. Both bands 8 and 9 arethus in particular cleaned from oxides at the flat sides which shall bebrought into mutual contact. Metal brushes or grinding discs can also beused for both bands 8 and 9 or also other components can be used throughwhich the described cleaning can be performed. The metal brushes 14 orgrinding discs 15 clean the surfaces of the two bands 8 and 9 incontinuous pass through and thus remove in particular oxide materials.The two bands 8 and 9 are simultaneously heated through the cleaningprocess to an adjustable temperature. The cleaned bands 8 and 9 whichare respectively metallically clean at their flat sides configured formutual contact are run to the compression device 4 through the channels17 and 18 which are connected with the cleaning device 3 and thecompression device 4 seamlessly. The bands 8 and 9 heated up as recitedsupra are brought into contact under pressure. Aluminum dust generatedthrough the cleaning process can be removed for safety reasons from thelower housing element 13 in particular time intervals. Two rollers 19and 20 are rotatably supported in the housing 16 of the compressiondevice 4 according to the illustrated embodiment. The two rollers 19 and20 are arranged in parallel with one another and separated by anadjustable gap. The size of the gap is adjustable through adjusting adistance of the rollers 19 and 20 from one another. The two bands 8 and9 are run in contact with one another through the gap between the tworollers 19 and 20 and thus compressed. Thus the two rollers 19 and 20are loaded with pressure. Instead of the rollers 19 and 20, thecompression device 4 can also be configured with a slot nozzle with anadjustable slot. The bands 8 and 9 are then run through the slot of theslot nozzle with the described method and pressed together so that theone piece band is produced.

The pressure imparted by the two rollers 19 and 20 or the slot nozzleupon the bands 8 and 9 can be adjusted so that the one piece band 11that is produced is simultaneously reduced in a thickness and thus withthe advantage by an amount which is between 5% and 20%. This measure onthe one hand side depends on the thickness of the bands 8 and 9 as basematerial and on the desired thickness of the one piece band as afinished, product.

1. A method for a metallurgically firm connection of an aluminum bandwith a copper band through which the two bands that are moved relativeto one another in their longitudinal direction are continuously cleanedfrom oxides in a cleaning device under protective gas at their contactsurfaces and are subsequently provided to a compression device in whichthe bands are pressed together with their clean contact surfaces andconnected with another to form a one-piece band comprising the steps of:running both bands continuously under protective gas up to and into thecompression device by configuring the cleaning device and thecompression device as a unit in a housing enclosing a contiguous space,and pulling the two bands or the one piece band through the cleaningdevice and the compression device through a pull off device arrangeddownstream of the compression device.
 2. The method according to claim1, wherein the bands are used with substantially identical widths.
 3. Adevice for performing the method according to claim 1, wherein tworollers are rotatably arranged in the compression device which areseparated from one another by a gap whose dimensions are variable,wherein the bands are pulled through the gap.
 4. The device forperforming the method according to claim 1, wherein the compressiondevice is configured as a slotted nozzle with a variable slot.
 5. Adevice for performing a metallurgically firm connection of an aluminumband with a copper band, comprising: a pull off device configured tomove the two bands relative to one another in their longitudinaldirection, a cleaning device for continuously cleaning oxides from thetwo bands under protective gas at their contact surfaces, and acompression device in which the two bands are pressed together withtheir clean contact surfaces and connected with each other to form aone-piece band, wherein the cleaning device and compression device areconfigured to run both bands continuously under protective gas up to andinto the compression device by configuring the cleaning device and thecompression device in a unit in a housing enclosing a contiguous space,and -wherein the pull off device pulls the two bands or the one pieceband through the cleaning device and the compression device, the pulloff device arranged downstream of the compression device.
 6. The devicefor performing the method according to claim 5, wherein the compressiondevice is configured as a slotted nozzle with a variable slot.